Abstract
Downy mildew caused by the oomycete Plasmopara viticola represents one of the most devastating diseases in vineyards. Current ways to control this disease rely mainly on fungicide applications, but agro-ecological concerns have raised interest in sustainable alternative methods. Certain rare sugars, like D-tagatose, have shown efficacy in reducing various plant diseases, including grapevine downy mildew. However, the mechanism of action of D-tagatose against grapevine downy mildew is not understood. The aim of this study was to characterize the efficacy and mechanism of action of a D-tagatose-based formulated product (IFP48) against grapevine downy mildew and compare it with the correspondent active molecule, pure D-tagatose (TAG). Whereas IFP48 root treatment provided scarce protection, the leaf treatment was the most efficient, especially at the dosage of 5 g/L. In particular, IFP48 treatment directly inhibited P. viticola sporangia germination, upregulated the expression of defense-related genes, and increased the content of stilbene phytoalexins. Conversely, the expression of defense-related genes and the content of stilbene phytoalexins were only slightly affected by TAG, suggesting that the formulation possibly improved D-tagatose effects against downy mildew in grapevine.
Highlights
Grapevine (Vitis vinifera L.) is susceptible to several diseases that can cause significant economic losses, including downy mildew, caused by Plasmopara viticola (Berk. andCurt.) Berl. and de Toni, which is currently managed mainly by repetitive fungicide treatments [1,2,3]
5 g/L, whereas the root treatment only generated a low level of protection
IFP48 directly inhibited the germination of P. viticola sporangia, controlled the expression of defense-related genes, and improved the content of stilbene phytoalexins
Summary
Grapevine (Vitis vinifera L.) is susceptible to several diseases that can cause significant economic losses, including downy mildew, caused by Plasmopara viticola (Berk. andCurt.) Berl. and de Toni, which is currently managed mainly by repetitive fungicide treatments [1,2,3]. De Toni, which is currently managed mainly by repetitive fungicide treatments [1,2,3]. Despite their efficiency, the misuse of agrochemicals has resulted in environmental pollution and public health risks [4]. Strategy of reducing the overall use of chemical pesticides by 50% in the EU, a drastic decrease in the number of fungicide applications must be accomplished in a relatively short period of time. To protect themselves from pathogenic threats, plants developed an immune system comprising constitutive and inducible resistance mechanisms [5]. Triggered resistance mechanisms enhance the plant capacity to defend against upcoming attacks of pests and pathogens [6,7,8]. Resistance induction can be assessed by analyzing various early and late defense responses, such as oxidative burst, ion fluxes, activation of mitogen-activated protein kinases, and upregulation of defense-related genes encoding pathogenesis related (PR) proteins and enzymes involved in phytoalexin synthesis [9,10,11] and carbohydrate metabolism [12]
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